Irrigation and aspiration are clinically important in many surgical procedures when fluids are selectively introduced into and removed from a target site within the body, usually while a surgery or other therapeutic medical procedure is performed. When the site of the therapeutic treatment is inside a body cavity or in the vasculature of the body, such as in a blood vessel, the irrigation and aspiration functions require special apparatus and methods. Surgical and percutaneous systems that both irrigate and aspirate have been developed, and some of these systems are catheter-based such that the introduction and removal of fluids is performed within an organ or a vessel by using the catheter as the conduit to introduce and remove fluids from a target site. As will be readily appreciated, the catheter allows the control elements to be remotely located, e.g., outside the body while the actual irrigation and aspiration functions are selectively provided within the body by selectively orienting the distal end of the catheter to the target site. In such cases, as is the case in open surgeries, the irrigation and aspiration functions accompany a therapeutic procedure that is performed at the target site along with the irrigation and aspiration.
Catheter-based irrigation and aspiration systems are unique in many respects due to their use in clinical situations where blockages or lesions exist inside a blood vessel, such as a coronary or carotid artery, and dangers arise from the creation and release of emboli within the vessel. In many intravessel therapeutic procedures, the danger from the creation of emboli is an unavoidable aspect of the therapeutic procedure. For example, lesions of atherosclerotic plaques inside a blood vessel are treated by several therapeutic procedures including endarterectomy, atherectomy, the placement of intravessel stents, balloon angioplasty, surgical ablation of the lesion, thrombectomy, OCT, dialysis shunt clearing and others. However, while each of these procedures has great therapeutic value in treating the lesion, each carries the risk of creating emboli during the procedure. As with any procedure conducted in the cardiovascular system, the risk is particularly great where plaque dislodged from inside a blood vessel can travel to the brain causing serious brain injury or death. For example, treating lesions of the carotids necessarily involve high risk. Currently, carotid treatments are attempted together with deployment of a filter to attempt to track emboli generated by or released from a carotid lesion. Unfortunately, crossing a carotid lesion with a filter or other structure can generate a cerebral ischemia or stroke. Schlueter et al. 2001, Circulation 104 (17) II-368. Moreover, studies have shown that merely crossing a carotid lesion with a guide wire can generate emboli. Al-Mubarak et al.: Circulation 2001 OCT 23:104 (17): 1999-2002. Also, some lesions carry such a high risk of generating emboli that therapeutic treatments are attempted only in the most severe cases. Where a chronic total occlusion exists, the diagnosis is particularly poor because it is impossible to place a structure distal of the occlusion such that emboli generated by the removal of the occlusion can be captured before circulating in the bloodstream. Such occlusions can only be treated by removing the occlusion from the proximal side, where emboli removal is uniquely difficult. Accordingly, if the capability existed to dramatically reduce the dangers of emboli creation during therapeutic procedures inside a vessel or organ of the body, the existing procedures would be safer and more widely practiced, and new procedures would be performed.
A variety of systems to contain and remove emboli have been proposed wherein a portion of a vessel that contains a lesion is segregated by two occluding members, typically two balloons, which are inflated proximate and distal to the lesion to effectively seal the inside of a region of the vessel containing a lesion prior to treatment of the lesion. Once treatment is complete, embolic particles such as dislodged plaque are removed by applying suction between the balloons. However, the tissue affected by a lesion is notoriously delicate and the treatment of the lesion has the capability to generate or release emboli whenever any mechanical manipulation of the lesion occurs. The generation and/or release of emboli is a concern virtually anytime a structure is passed through a susceptible vessel. Such circumstances include the placement of a balloon or stent, the placement of a filter, or simply the use of a catheter or guide wire for imaging, diagnostic, or any other procedure. In many procedures, the internal portion of a vessel is occluded to provide a segregated region of a vessel through which fluid does not flow. Moreover, virtually anytime structures are inserted into the vessel, the generation of release of emboli is a concern. For example, in the common practice of placing a stent inside an artery, a filter may be placed distally of the stent to attempt to collect emboli generated when the stent is expanded to engage plaques or lesions inside the vessel. All devices placed distal involve the crossing of the lesion. All crossings of lesions create emboli of some quantity and significance. Such systems cannot protect the patient against the potential harm inherent in the placing the device. Additionally, once the stent is in place, the filter must be removed by pulling it through the portion of the vessel in which the stent has been inserted. This carries the risk that the filter will impact the vessel and cause the release of emboli and/or contact the stent and either displace the stent or similarly cause the release of embolic particles. The use of occluding members of any type has certain drawbacks. Anytime a structure is used as an occlusive member inside a vessel, the structure must deform the vessel from the inside to create a seal about the periphery thereof with the internal surface of the vessel. For example, to make the seal tight enough to prevent the passage of fluid and emboli past the balloon, the expansion of the balloon typically deforms the vessel outward and may disrupt plaque in and about the point of contact between the vessel and the balloon. Moreover, any plaque that becomes dislodged outside the barrier formed by the balloon is released into the blood stream because there is no mechanism distal of the balloon to remove the emboli. For this reason, irrigation and aspiration proximate to the lesion are particularly important.
To create a segregated region of a vessel, a two-balloon system may be used. However, certain disadvantages of a two-balloon system also arise from the placement of balloons on both sides of a lesion and the nature of the blood flow that occurs in the region of the vessel containing the lesion once the balloon is removed. At the point of contact between the balloon and the vessel, plaque may be compressed underneath the balloon and may become dislodged upon reestablishment of flow through the vessel. Furthermore, many clinicians have observed that the region distal of a lesion is more likely to exhibit plaque formation than the region proximal of a lesion. Thus, the use of an occluding member distal of a lesion does not eliminate the risk of creating emboli that may enter the vessel. The risk is particularly great when a second balloon is used because the balloon is not advantageously placed for the removal of emboli created by the use of the balloon itself and because the balloon must be removed by passing it across the lesion upon completion of a procedure. This drawback is present in all circumstances when a balloon is advanced across a lesion because, when any occluding member is placed distally of the lesion, the occluding member must be drawn back across the lesion to remove the occluding member at the end of a procedure. Each passage of an occluding member across the lesion, even in a retracted or deflated state, carries a substantial risk that additional emboli will be produced.
Also, the placement of two balloons requires additional time to inflate the second balloon and adds to the complexity of a device due to an additional lumen that must be incorporated into the catheter to inflate the balloon. In a finite number of cases, the occluding member that is distal of a lesion, and is required to retain emboli in a defined area within the vessel, has been observed to fail, thereby releasing the emboli into the bloodstream. Because the second balloon is relied upon to prevent the flow of emboli past the region of the vessel containing the lesion, the failure of the balloon is a critical event that threatens the health of a patient undergoing the procedure. Furthermore, due to geometric constraints, the second balloon often acts as the guide wire as well. When delivering tools to perform the therapeutic or diagnostic procedure within the vessel, the balloon may move and disrupt the vessel wall. Introduction of tools and other manipulations of a distally located balloon can also result in deflating the balloon or otherwise causing the balloon to lose patency on the interior of the vessel.
Anytime that a balloon is placed distal to a lesion, the contact between the balloon and the lesion carries the risk of damaging the vessel. For these reasons, the use of balloons inside the vessel is preferred to be minimized and the length of time and extent of contact between a balloon and the inside of a vessel should be reduced. Ideally, the balloon or other occluding member could be placed proximal to a lesion so that the area containing the lesion would be isolated. To achieve this, the irrigation and aspiration functions would have to be provided by a structure that is positioned distal of the occluding element, such that the occluding element could be placed proximal of the lesion, and the aspiration and irrigation functions achieved distal of the occluding member.
Even under existing technologies where aspiration and irrigation are applied in a catheter based system, the parameters of fluid flow, as well as the placement of the aspiration and irrigation ports relative to an occluding member, are important to the physiological outcome for any given procedure. For example, removal of fluid and/or embolic particles by simple suction from within a body conduit may only remove a portion of the fluid present in the vessel and may leave emboli in place even if all of the fluid is removed and replaced. Deposits of plaque and other debris that may exist inside a vessel have a tendency to adhere to one another and particulate emboli tend to adhere to the sidewalls of the vessel. Thus, a system that provides limited fluid exchange is particularly unlikely to achieve a complete removal of emboli. Also, given that the interior walls of a vessel may have been contacted from within during a therapeutic procedure, a high likelihood exists that additional particles may be dislodged upon the establishment of a robust fluid flow through the vessel.
Ideally, a system for aspirating and irrigating the interior or a vessel or organ would provide both fluid exchange and fluid flow parameters that are at least similar to that experienced during ordinary physiological functions and preferably would create a turbulent fluid flow that would proactively assist in the removal of particles and other emboli. Such a system would require both a catheter element that achieved aspiration and irrigation as well as a fluid exchange apparatus that would be coupled with the catheter to produce the desired fluid flow rates and other fluid parameters. Because of the wide variation in intravessel procedures and the location of disease, an irrigation and aspiration system would also be particularly useful if the catheter element could be selectively positioned along a specified length of a vessel where emboli may be created together with operation of the fluid exchange apparatus to control the irrigation and aspiration flow. This capability in the catheter element is most readily created with only a single balloon system having a separate, movable, irrigation and aspiration catheter.
In the prior art two-balloon system described above, where a region of a vessel is segregated by a pair of balloons located both proximally and distally of a lesion, the area of fluid flow is limited to the region defined by the placement of the two balloons. The problem is particularly acute when a vessel is treated with a procedure that installs a stent or manipulates the plaque in a vessel, such as with an angioplasty, where the lesion is physically manipulated as part of the therapeutic treatment. Assuming that the therapeutic treatment is successful, the vessel is treated by virtue of expanding the interior volume and promoting the flow of blood through the vessel. Under these circumstances, the portions of the vessel distal of the lesion have been contacted by a balloon and are then exposed to a higher volume of fluid flow than existed before the procedure. In the context of a typical patient, a vessel which had become slowly blocked due to the deposit of plaque over a large number of years has been expanded by the treatment of the lesion and this therapeutic treatment at an upstream point subjects the region in which the lesion is located and those downstream internal portions to a rate and volume of blood flow that has not been experienced in the many years since the vessel began to become occluded. Under these circumstances, an additional risk exists that plaques located downstream from the lesion will be dislodged and will enter the circulation causing serious injury.
As with ordinary irrigation and aspiration in an open surgery, the irrigation and aspiration that are applied through existing catheter systems are typically regulated only by setting the positive or negative pressure that is applied to the aspiration or irrigation lumen of the catheter and is in turn communicated to the distal end of the catheter to insert or remove fluid respectively. However, to create the specific fluid flow parameters that maximize the removal of emboli and the fluid displacement within a vessel, thereby establishing fluid change in the vessel in the most physiologically relevant manner, a specialized fluid exchange device would have to be created to regulate the fluid flow parameters of both the irrigation and aspiration functions of the system.
An ideal irrigation and aspiration system could be an additive component to several other apparatus that are used in therapeutic, diagnostic, or imaging applications in the body such that the capability of the system would not be exclusive of other technologies that have been applied to enhance the safety of an intravessel procedure. Several different approaches apart from irrigation and aspiration have been attempted to physically capture emboli downstream at a lesion, most notably through the use of filters. However, filters have inherent drawbacks that cannot be completely eliminated. For example, embolic particles smaller than the filter pore size, commonly on the order of 100 microns evade filters, which must not be so small that physiologically important elements such as red and white blood cells are captured by the filter. Also, particles larger than the pore size tend to become trapped in the filter such that the filter itself becomes an occlusive element and blood flow through the filter is impeded. Also, as described above for occluding structures, whenever a filter is introduced distally to the lesion in a vessel, a finite probability exists that the removal of the filter will generate emboli. Still further, where a stent is placed at a lesion, the movement of the filter past the stent and through the vessel has the capability to catch or displace the stent.
Although certain portions of the discussion herein are directed towards a preferred embodiment of the apparatus of the invention used in an intravessel procedure, the devices and methodologies of the invention can readily be applied to non-vessel sites within the body such as within any body conduit such as an ear canal, colon, intestine, the trachea, lung passages, sinus cartilages, or any internal volume wherein a controlled and localized irrigation and aspiration function are desired. For example, in a diagnostic colonoscopy an endoscope may be introduced to aid in optical visualization of the site. However, the colon responds to fluid pressure changes and thus while trying to clear the field the tissue of note may move. To aid in this diagnostic situation, a controlled introduction of a clear fluid could be introduced in concert with an equivalent aspiration of dirty fluid. As such, the tissue may remain in the field of view while the process occurs. For imaging purposes the introduction of a contrast agent while simultaneously extracting an equivalent fluid will allow a vessel or organ to maintain its normal fluid level and pressure. As the imaging is completed, the same system could then return a more normal fluid to the site while extracting the foreign contrast agent. Imaging “pig-tail” catheters are presently used to introduce contrast agents to vascular system, even though radiopaque contrast agents are known to maintain a level of toxicity (Solomon, Kidney International, 1998, vol. 53, pp. 230-242). If the field of contrast was introduced and extracted as proposed by Courtney, et al., the patient's exposure would be substantially reduced.